1. Field of the Invention
The invention relates generally to a hockey stick for use in playing hockey, the stick being of the type having a shaft and a replaceable blade, which blade is firmly affixed to the shaft for play, and which blade is loosened to allow changing of the blade by application of heat to the hockey stick at the juncture of the replaceable blade and the shaft. The invention more specifically relates to an improved system for releasably joining the blade to the shaft in such sticks.
2. Description of the Related Art
Hockey sticks for playing the game of hockey historically were made of wood and included a shaft and a blade. More recently, advances in the art have given rise to hockey sticks having components formed of other materials, such as aluminum and composite materials, for example fiber/resin composites incorporating epoxy and graphite. These newer materials are used because they give rise to advantages in weight and balance of the hockey stick and in its flexural properties. Replaceable blades are another more recent advance, and are generally formed of wood overlaid with a composite material such as fiberglass to strengthen the blade and provide increased durability. The blade is also often made of a polymer resin or a composite, which may also contain a fiber filler for example, to give increased strength and wear resistance. Such blades have a shank, or tennon, portion which is inserted into and interfits with a socket formed by an open end of the shaft of known hockey sticks. Such sockets are generally rectangular in shape, to match the shaft and to prevent twisting of the blade with respect to the shaft. The tennon must be securely held in the shaft, as "fly out" of a blade during play is highly undesirable.
Blades must be changed periodically due to wear or damage. In the most widely used configuration, the shank is held within the socket and is thus attached to the shaft by the use of a thermoplastic adhesive, commonly known as a "hot melt" glue. Conventionally, such a hot melt glue is liquefiable at temperatures well above that normally encountered in using a hockey stick and conventionally requires use of a high temperature heat source such as an electric heater recommended by the manufacturer, or by use of a torch which is often employed regardless of manufactures' recommendations and warnings to the contrary. When liquified by application of heat, such an adhesive allows removal or installation of a blade; and when allowed to cool, solidifies and adhesively bonds together the shaft and the shank of the blade.
Generally, manufacturers of hockey sticks recommend specific methodologies for heating the shaft of the hockey stick at the location of the hot melt glue-bonded connection at the end of the shaft. Such methodologies feature limiting the maximum temperature of the shaft to a material dependent value which allows liquefaction of the thermoplastic adhesive but is not injurious to the material from which the hockey stick shaft is made. Certain materials, specifically composite materials commonly used in forming the shaft, are susceptible to damage and weakening as a result of heating them to high temperatures, such as may be occasioned by using a torch or other open flame for example, to heat the shaft in carrying out a blade change, for example.
However, it is often desirable to change a blade quickly, and when using a hot melt glue connection recommended methods of heating the shaft to effect a blade change take a relatively long time. Consequently, faster ways of heating are commonly employed by hockey players to heat the end of the shaft regardless of manufactures' recommendations and warnings. Particularly, during a game, players in a hurry to change a damaged blade, for example, may use a high temperature heat source such as a propane torch or the like, providing a rapid transfer of heat energy to the shaft to facilitate a faster blade replacement. Use of a torch is universally recognized as hazardous, and accordingly neither method is without drawbacks. Common to both is the necessity to heat the shaft to a high temperature, which in-and-of-itself is not ideal.
When using a flame to heat a shaft-blade connection of a composite shaft hockey stick, degradation of the structural properties important to strength and flexibility of the shaft often results, and breaking of such hockey sticks along the shaft at such a damaged location has been observed. The dangers attendant a hockey stick breaking in this manner during play are well known. At the least, such a damaged hockey stick may be rendered unusable when it is recognized that the portion of the shaft which receives the blade shank has been damaged, and a tight and reliable union between the shaft and the blade cannot thereafter be accomplished. Shafts formed of metals can also be damaged by overheating, for example by cracks which may develop due to stress induced by heating and cooling to and from a relatively higher temperature and by differential heating, which cracks may later propagate.
Lastly, using a torch or electric heater to effect a blade change is inconvenient. Moreover, it may limit the places where a blade can be changed due to availability of an electric power source, or due to regulations regarding open flames in buildings or certain outdoor areas for example. Also, added equipment costs to the player or sponsor results from the requirement to purchase and use the additional equipment required to carry out one of these heating methods.
The above concerns being recognized, there is an opportunity to advance the art by providing a hockey stick of the type having a replaceable blade which provides the advantageous properties of newer metal and composite materials, yet which allows repeated blade changes without the need for application of heat at very high temperatures, such as from a torch for example, but instead at much lower temperatures. The present invention is directed to such an advance.